Certain undesirable physiological manifestations, such as acne vulgaris, seborrhea, female hirsutism, androgenic alopecia which includes female and male pattern baldness, and benign prostatic hyperplasia, are the result of hyperandrogenic stimulation caused by an excessive accumulation of testosterone ("T") or similar androgenic hormones in the metabolic system. Androgenic alopecia is also known as androgenetic alopecia. Early attempts to provide a chemotherapeutic agent to counter the undesirable results of hyperandrogenicity resulted in the discovery of several steroidal antiandrogens having undesirable hormonal activities of their own. The estrogens, for example, not only counteract the effect of the androgens but have a feminizing effect as well. Non-steroidal antiandrogens have also been developed, for example, 4'-nitro-3'-trifluoromethyl-isobutyranilide. See Neri, et al., Endocrinol. 1972, 91 (2). However, these products, though devoid of hormonal effects, compete with all natural androgens for receptor sites, and hence have a tendency to feminize a male host or the male fetus of a female host and/or initiate feed-back effects which would cause hyperstimulation of the testes.
The principal mediator of androgenic activity in some target organs, e.g. the prostate, is 5.alpha.-dihydrotestosterone ("DHT") , formed locally in the target organ by the action of 5.alpha.-reductase, which converts testosterone to DHT. Inhibitors of 5.alpha.-reductase will serve to prevent or lessen symptoms of hyperandrogenic stimulation in these organs. See especially U.S. Pat. Nos. 4,377,584, issued Mar. 22, 1983, and 4,760,071, issued Jul. 26, 1988, both assigned to Merck & Co., Inc. It is now known that a second 5.alpha.-reductase isozyme exists, which interacts with skin tissues, especially in scalp tissues. See, e.g., G. Harris, et al., Proc. Natl. Acad. Sci. USA, Vol. 89, pp. 10787-10791 (November 1992). The isozyme that principally interacts in skin tissues is conventionally designated as 5.alpha.-reductase 1 (or 5.alpha.-reductase type 1), while the isozyme that principally interacts within the prostatic tissues is designated as 5.alpha.-reductase 2 (or 5.alpha.-reductase type 2).
Since 5.alpha.-reductase type 1 and type 2 convert testosterone to DHT, inhibition of either or both of the isozymes would serve to alleviate the conditions and diseases mediated by DHT. The present invention addresses this by providing novel compounds that are active as inhibitors of 5.alpha.-reductase type 1.